Centrifugal fan



Nov. 30, 1943. w. J. CALDWELL CENTRIFUGAL FAN Fild March 10, 1942 2 ShetS-Shee t 1 William JUaZJweZL, 51

Nov. 30, 1943. w. J. CALDWELL CENTRIFUGAL FAN Filed March 10, 1942 2Sheets-Sheet 2 Patented Nov. 30, 1943 UNITED STATES PATENT OFFICECENTRIFUGAL FAN William J. Caldwell, Independence, Mo. Application March10, 1942, Serial No. 434,095

Claims. (01. 230134) My invention relates to centrifugal fans and oneobject of the invention is the provision of a new and efiicient fan ofthis character whereby an air blast of maximum volume and density may bedelivered at high velocity with a minimum expenditure of power.

Another object is the provision of an impeller having blades of novelshape to progressively compress and accelerate the flow of air from theinlet to the outlet of the fan housing and to discharge it at highvelocity in a compact stream.

A still further object is the provision of a high speed fan having animpeller which effects sufiicient air compression in both the impellerand the housing to largely negative the air noise which restrictsconventional fans to low or medium velocities.

Another object is the provision of an impeller having blades adjustablymounted so that each may be inclined forwardly relative to a radial lineto increase the pressure and velocity of the air, or inclined rearwardlyof said radial line to lower the pressure and increase the volume of theair flow, thereby making available a wide range of performance with thesame component parts of the impeller.

A further object is the provision of a housing having an adjustable gatewhereby the volume of air discharged from the housing can be regulatedas desired.

Another object is the provision of a housing which is adjustably mountedso that it may be turned axially to discharge an air blast either in ahorizontal plane, or at various angles to such plane.

Another object is the provision of a centrifugal fan which is soconstructed that its component parts can be economically manufacturedand assembled.

Other objects will hereinafter appear and in order that the inventionmay be fully understood, reference will now be had to the accompanyingdrawings in which:

Fig. l is a side elevation of the fan with some of the parts brokenaway.

Fig. 2 is a front elevation of the fan.

Fig. 3 is a side elevation of the impeller with some of the bladesremoved.

Fig. 4 is an enlarged detail of part of one blade.

Fig. 5 is a plan view of one of the blades mounted upon a spoke.

Fig. 6 is a fragmentary vertical section of the housing and part of itsmounting, on line 6-6 of Fig. 1.

Fig. '7 is a fragmentary detail of a modified form of impeller.

In carrying out the invention I provide a housing 2 comprising acircumferential wall 4 and two side walls 6, which latter have large airinlets 8. A discharge nozzle I0 is provided through which an air blastmay be discharged from the forward portion of the housing.

When installing the fan for use it may be found desirable to point thenozzle ID in other directions than the horizontal plane as shown by Fig.1, so I mount the housing 2 in such manner that it may be turnedaxially. his is accomplished by providing one of the side walls 6 with aring 12 which is welded or otherwise appropriately fixed to said wall inconcentric relation to the associated air inlet'8 and rotatably mountsaid ring in the channel of a stationary ring l4 fixed to the flanges I6of a housing base l8. The ring l2 may be secured against rotation in thechannel of the companion ring M by any appropriate means, such, forinstance as a plurality of bolts 20 which extend through transverseregistering holes in the rings l2 and I4.

Referring now more particularly to the' rotary impeller 22 forming animportant feature of the invention, 23 designates a hub provided withradial spokes 26 and reinforced with centrally-disposed, oppositelyarranged, annular shoulders 28 fixed upon a shaft 30 extendingtransversely through the housing 2. The shaft 30 is concentric with therings I2 and I4 and may be driven by an electric motor, pulley, or otherconventional driving means, not shown. The shaft 30 may be mounted insuitable bearings, not shown, or if driven by an electric motor may becoupled directly to and driven by the motor shaft.

The impeller 22 includes a plurality of blades 36 which are adjustablyassociated with the spokes 26, for a purpose which will hereinafterappear. Each blade may be made in one piece, but in the present instanceI have shown each blade comprising two members 31 mounted on oppositesides of the hub 24 and the associated spoke 26. Each blade 36 isadjustably connected at its inner end to the hub 24 by any appropriatemeans, such as a pivot 38, and connected at its outer end to the spoke26 by a bolt 40 which extends through an arcuate slot 42 concentric withthe shaft 36 and extending through the spoke. The outer end of eachmember 31 is bent backward at, substantially, right angles as indicatedat 44 and terminates at its rear end in an outturned offset vane 46. Themembers 31 diverge towards their leading edges to provide a V- shapedair channel d3, which faces the direction of travel and extends from theinner end of the blade to the rearwardly bent portions M. Although Iprefer to make the blade V-shaped it may be of concave or U-crosssection. The impeller 22 is of slightly less diameter than either of theair inlets 8, so that it can be readily installed in the housing 2.

A flexible gate 50 of approximately inverted V- form is adjustablymounted in the forward portion of the housing 2 to regulate the volumeof air discharged through the nozzle ll). In the present instance I haveprovided the respective legs of the gate with bolts and 52 adjustablymounted in slots 53 and 54 in the circumferential wall 4 of the housingand the bottom wall of the'nozzle It. The bolts 5i and 52 are secured intheir adjusted positions by nuts 55 and 56, respectively.

In practice, when the impeller 22 is rotating at normal speed it createsa suction that draws air into housing 2 through the inlets 8. As theimpeller blades 35 impinge against the inflowing air it is compressedinto the channels 48 and progressively accelerated and then ejected fromthe outer ends of said channels by centrifugal force into the path ofthe respective vanes 46 which further compress and accelerate the airand discharge it at a high velocity in the form of a dense stream fromthe housing 2 through nozzle [6.

The V-shape of the blade adds to its stability and forces the air to thecenter of the channel 56, thereby reducing side slippage of the air andincreasing the efiiciency of the blade. By pivotally mounting the bladeit may be adjusted forward relative to a radial line a, Fig. 3, toincrease the velocity-pressure of the air stream, and by adjusting theblade rearward relative to said radial line the pressure is reduced andthe volume of the air flow is increased. Thus it will be understood thatI have provided an impeller whereby control of the air stream may bevaried by adjusting some of the component parts of the impeller.v

By tapering the blades towards their inner ends as shown in thedrawings, their weight and centrifugal loading on the impeller isreduced.

Fig. 7 shows a fragmentary portion of a modified form of impeller inwhich the blade 36a comprises a single member 3'ia, secured to one sideof the hub 24a which is enlarged diametrically to dispense with thespokes 25 and cooperate with the single blade member 31a in providingthe channel 48a.

While I have shown two forms of the invention, I reserve all rights tosuch forms and modifications thereof as properly fall within the scopeof the claims.

Having thus described my invention, what I claim and desire to secure byLetters Patent, is:

1. In a centrifugal fan, an impeller comprising rotary supporting means,a series of radial blades pivotally mounted upon said rotary supportingmeans to permit forward or backward adjustment relative to a radial lineextending through each blade, and means for securing each blade inadjusted position.

2. In a centrifugal fan, an impeller comprising rotary supporting means,a series of blades radially disposed with respect to said rotarysupporting means, pivotal means connecting the inner end of each bladeto the rotary supporting means to permit inclination of the bladeforward or backward relative to a radial line extending through eachblade, and means near the outer free end of each blade for securing thesame in adjusted position.

3. A centrifugal fan system comprising a housing having an air inlet andan air outlet, and a rotary impeller in said housing including a seriesof blades spaced about the axis of the impeller to progressivelyaccelerate the flow of air from the inlet to the outlet of the housing,each blade being of approximately V-cross section to provide a channelextending longitudinally of the blade and into which air is compressedand then ejected from the outer end of said channel in a compact streamby centrifugal force, means whereby each blade may be inclined forwardor backward relative to a radial line extending through each blade, anda transverse outturned vane at the outer end of each blade adapted toimpinge against the ejected air stream to furtherincrease accelerationthereof and direct the stream against the circumferential wall of thehousing, the exact angle of the discharge being controlled by thecurvature of the vane and the angle at which the blade is adjustedforward or backward of a radial line.

4. In a centrifugal fan, rotary means, and a blade suitably secured tosaid rotary means and bent to project therefrom at an angle to providean air channel extending longitudinally of the blade, the outer part ofsaid blade being bent backward at approximately right angles to the mainportion of the blade and terminating in an outturned vane which extendstransversely to the axis of the rotary means.

5. In a centrifugal fan, an impeller comprising rotary means, and aseries of radial blades each comprising two members secured to oppositesides of said rotary means and bent in opposite directions to provide anair channel, the outer part of each member being bent backward andterminating in an outturned vane which extends transversely to the axisof the rotary means.

WILLIAM J CALDWELL.

